With development of mobile Internet and popularization of intelligent terminals, data traffic shows an explosive growth tendency. A WLAN (wireless local area network) becomes one of mainstream mobile broadband access technologies owing to its advantages in aspects of a high rate and low costs.
Generally, a WLAN system includes a primary channel and multiple secondary channels. Currently, bandwidths of the primary channel and the secondary channels are all 20 MHz, which is referred to as “basic bandwidth”. A WLAN system complying with the 802.11n protocol (“802.11n system”) can support 40 MHz multi-channel transmission, that is, a 40 MHz channel including one primary channel and one secondary channel is selected to perform data transmission. For an 802.11ac system, the system can support 160 MHz or 80+80 MHz multi-channel transmission.
In a WLAN system, at a MAC (Media Access Control) layer, data transmission is generally performed by using the CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance, carrier sense multiple access with collision avoidance) competition mechanism. A WLAN node that is to send data, such as a STA (Station) or an AP (Access Point) performs carrier sense before sending data. If it is detected that energy of a channel exceeds a CCA (Clear Channel Assessment) threshold, the channel is considered to be busy, and the node does not send data on the channel; or if it is detected that energy of a channel is less than the CCA threshold, the channel is considered to be idle, and the node performs channel contention.
Currently, a WLAN system that supports multi-channel transmission, such as the 801.11n system and the 802.11ac system usually determines whether a channel is available according to a busy/idle state of the primary channel. For example, for the 802.11n system, a common CCA detection solution includes: Signal detection is used on the 20 MHz primary channel, and if detected signal energy is less than −82 dBm, it is considered that the 20 MHz primary channel is idle; energy detection is used on a 20 MHz secondary channel, and if detected signal energy is less than −62 dBm, it is considered that the 20 MHz secondary channel is idle; if both the 20 MHz primary channel and the 20 MHz secondary channel are in an idle state, an STA may perform 40 MHz multi-channel transmission.
The next-generation WiFi (Wireless Fidelity) 802.11ax protocol supports more flexible system bandwidth. Different from the 802.11ac system and the 802.11n system, an 802.11ax system uses an OFDMA mechanism. Therefore, use of system bandwidth is more flexible, and high bandwidth is more frequently used for transmission. If the foregoing CCA detection solution is still used, determining whether a channel is available depending on a busy/idle state of a primary channel greatly limits use of high bandwidth.